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Spray foam roof rafters

user-7330770 | Posted in General Questions on

So I have been doing a lot of research I’m planning on spraying the roof rafters. When spray foaming the roof rafters do you vent the attic or not?

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, can you tell us your name? (I'm Martin.)

    The contractors who are installing the spray foam need to make sure than any room where they are working is properly ventilated during and after the installation process. For more information on this issue, see "Spray Foam Jobs With Lingering Odor Problems."

    If you are interested if installing spray foam on the underside of the roof sheathing, so that the insulation follows the sloped roofline of the attic, then the attic should not be vented after the installers have left the site and the spray foam has had time to fully cure. (You described the proposed work as "spraying the roof rafters," but I assume you meant "the underside of the roof sheathing" rather than "the roof rafters.")

    If the existing attic has soffit vents and a ridge vent, these vents would be sealed by the spray foam installer. (Leaving these vents open would invite outdoor air inside, defeating the purpose of your insulation.)

    For more information on this issue, see "Creating a Conditioned Attic."

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